Mapping mesh generation is widely applied in pre-processes of Finite Element Method （FEM）. In this study, the basic 3D mapping equations by Lagrange interpolating function are founded. Based these equations, a mappi...Mapping mesh generation is widely applied in pre-processes of Finite Element Method （FEM）. In this study, the basic 3D mapping equations by Lagrange interpolating function are founded. Based these equations, a mapping pattern library, which maps essential configurations e.g. line, circle, rotary body, sphere etc. to hexahedral FEM mesh, has been built. Then available FEM mesh will be generated by clipping and assembling the mapped essential objects. Study case illustrates that the proposed method is simple and efficient to generate valid FEM mesh for complex 3D engineering structure.展开更多
The finite element(FE)-based simulation of welding characteristics was carried out to explore the relationship among welding assembly properties for the parallel T-shaped thin-walled parts of an antenna structure.The ...The finite element(FE)-based simulation of welding characteristics was carried out to explore the relationship among welding assembly properties for the parallel T-shaped thin-walled parts of an antenna structure.The effects of welding direction,clamping,fixture release time,fixed constraints,and welding sequences on these properties were analyzed,and the mapping relationship among welding characteristics was thoroughly examined.Different machine learning algorithms,including the generalized regression neural network(GRNN),wavelet neural network(WNN),and fuzzy neural network(FNN),are used to predict the multiple welding properties of thin-walled parts to mirror their variation trend and verify the correctness of the mapping relationship.Compared with those from GRNN and WNN,the maximum mean relative errors for the predicted values of deformation,temperature,and residual stress with FNN were less than 4.8%,1.4%,and 4.4%,respectively.These results indicate that FNN generated the best predicted welding characteristics.Analysis under various welding conditions also shows a mapping relationship among welding deformation,temperature,and residual stress over a period of time.This finding further provides a paramount basis for the control of welding assembly errors of an antenna structure in the future.展开更多
A physical value mapping （PVM） algorithm based on finite element mesh from the stamped part in stamping process to the product is presented, In order to improve the efficiency of the PVM algorithm, a search way from...A physical value mapping （PVM） algorithm based on finite element mesh from the stamped part in stamping process to the product is presented, In order to improve the efficiency of the PVM algorithm, a search way from the mesh of the product to the mesh of the stamped part will be adopted. At the same time, the search process is divided into two steps： entire search （ES） and local search （LS）, which improve the searching efficiency. The searching area is enlarged to avoid missing projection elements in ES process. An arc-length method is introduced in LS process. The validity is confirmed by the results of the complex industry-forming product.展开更多
The scaled boundary finite element method(SBFEM) is a semi-analytical numerical method,which models an analysis domain by a small number of large-sized subdomains and discretises subdomain boundaries only.In a subdoma...The scaled boundary finite element method(SBFEM) is a semi-analytical numerical method,which models an analysis domain by a small number of large-sized subdomains and discretises subdomain boundaries only.In a subdomain,all fields of state variables including displacement,stress,velocity and acceleration are semi-analytical,and the kinetic energy,strain energy and energy error are all integrated semi-analytically.These advantages are taken in this study to develop a posteriori h-hierarchical adaptive SBFEM for transient elastodynamic problems using a mesh refinement procedure which subdivides subdomains.Because only a small number of subdomains are subdivided,mesh refinement is very simple and efficient,and mesh mapping to transfer state variables from an old mesh to a new one is also very simple but accurate.Two 2D examples with stress wave propagation were modelled.The results show that the developed method is capable of capturing propagation of steep stress regions and calculating accurate dynamic responses,using only a fraction of degrees of freedom required by adaptive finite element method.展开更多
To study the hot deformation behavior of Mg-8.3 Gd-4.4 Y-1.5 Zn-0.8 Mn(wt%) alloy,hot compression tests were conducted using a Gleeble-3500 thermal simulator at temperatures ranging from 653 to773 K,true strain rates ...To study the hot deformation behavior of Mg-8.3 Gd-4.4 Y-1.5 Zn-0.8 Mn(wt%) alloy,hot compression tests were conducted using a Gleeble-3500 thermal simulator at temperatures ranging from 653 to773 K,true strain rates of 0.001-1 s^(-1),and a deformation degree of 60%.Results of hot compression experiments show that the flow stress of the alloy increases with the strain rate.The true stress-true strain curves are corrected by correcting the effect of temperature rise in the deformation process.Activation energy,Q,equal to 287380 J/mol and material constant,n,equal to 4.59 were calculated by fitting the true stress-true strain curves.Then,the constitutive equation was established and verified via finite element simulation.Results of the hot processing map show that the probability of material instability increases with the degree of deformation,which indicates that the material is not suitable for large deformation in a single pass.On the whole,the alloy is appropriate for multipass processing with small deformation and a suitable processing temperature and strain rate are 733 K and 0.01 s-1,respectively.展开更多
Axially heterostructured nanowires are a promising platform for next generation electronic and optoelectronic devices.Reports based on theoretical modeling have predicted more complex strain distributions and increase...Axially heterostructured nanowires are a promising platform for next generation electronic and optoelectronic devices.Reports based on theoretical modeling have predicted more complex strain distributions and increased critical layer thicknesses than in thin films,due to lateral strain relaxation at the surface,but the understanding of the growth and strain distributions in these complex structures is hampered by the lack of high-resolution characterization techniques.Here,we demonstrate strain mapping of an axially segmented GalnP-lnP 190 nm diameter nanowire heterostructure using scanning X-ray diffraction.We systematically investigate the strain distribution and lattice tilt in three different segment lengths from 45 to 170 nm,obtaining strain maps with about 10^-4 relative strain sensitivity.The experiments were performed using the 90 nm diameter nanofocus at the NanoMAX beamline,taking advantage of the high coherent flux from the first diffraction limited storage ring MAX IV.The experimental results are in good agreement with a full simulation of the experiment based on a three-dimensional(3D)finite element model.The largest segments show a complex profile,where the lateral strain relaxation at the surface leads to a dome-shaped strain distribution from the mismatched interfaces,and a change from tensile to compressive strain within a single segment.The lattice tilt maps show a cross-shaped profile with excellent qualitative and quantitative agreement with the simulations.In contrast,the shortest measured InP segment is almost fully adapted to the surrounding GalnP segments.展开更多
In this paper,we present the Multiscale Finite Element Method(MsFEM)for problems on rough heterogeneous surfaces.We consider the diffusion equation on oscillatory surfaces.Our objective is to represent small-scale fea...In this paper,we present the Multiscale Finite Element Method(MsFEM)for problems on rough heterogeneous surfaces.We consider the diffusion equation on oscillatory surfaces.Our objective is to represent small-scale features of the solution via multiscale basis functions described on a coarse grid.This problem arises in many applications where processes occur on surfaces or thin layers.We present a unified multiscale finite element framework that entails the use of transformations that map the reference surface to the deformed surface.The main ingredients of MsFEM are(1)the construction of multiscale basis functions and(2)a global coupling of these basis functions.For the construction of multiscale basis functions,our approach uses the transformation of the reference surface to a deformed surface.On the deformed surface,multiscale basis functions are defined where reduced(1D)problems are solved along the edges of coarse-grid blocks to calculate nodalmultiscale basis functions.Furthermore,these basis functions are transformed back to the reference configuration.We discuss the use of appropriate transformation operators that improve the accuracy of the method.The method has an optimal convergence if the transformed surface is smooth and the image of the coarse partition in the reference configuration forms a quasiuniform partition.In this paper,we consider such transformations based on harmonic coordinates(following H.Owhadi and L.Zhang[Comm.Pure and Applied Math.,LX(2007),pp.675-723])and discuss gridding issues in the reference configuration.Numerical results are presented where we compare the MsFEM when two types of deformations are used formultiscale basis construction.The first deformation employs local information and the second deformation employs a global information.Our numerical results showthat one can improve the accuracy of the simulations when a global information is used.展开更多
基金Supported by the National Natural Science Foundation of China (A10102006)
文摘Mapping mesh generation is widely applied in pre-processes of Finite Element Method （FEM）. In this study, the basic 3D mapping equations by Lagrange interpolating function are founded. Based these equations, a mapping pattern library, which maps essential configurations e.g. line, circle, rotary body, sphere etc. to hexahedral FEM mesh, has been built. Then available FEM mesh will be generated by clipping and assembling the mapped essential objects. Study case illustrates that the proposed method is simple and efficient to generate valid FEM mesh for complex 3D engineering structure.
基金The Natural Science Foundation of Jiangsu Province,China(No.BK20200470)China Postdoctoral Science Foundation(No.2021M691595)Innovation and Entrepreneurship Plan Talent Program of Jiangsu Province(No.AD99002).
文摘The finite element(FE)-based simulation of welding characteristics was carried out to explore the relationship among welding assembly properties for the parallel T-shaped thin-walled parts of an antenna structure.The effects of welding direction,clamping,fixture release time,fixed constraints,and welding sequences on these properties were analyzed,and the mapping relationship among welding characteristics was thoroughly examined.Different machine learning algorithms,including the generalized regression neural network(GRNN),wavelet neural network(WNN),and fuzzy neural network(FNN),are used to predict the multiple welding properties of thin-walled parts to mirror their variation trend and verify the correctness of the mapping relationship.Compared with those from GRNN and WNN,the maximum mean relative errors for the predicted values of deformation,temperature,and residual stress with FNN were less than 4.8%,1.4%,and 4.4%,respectively.These results indicate that FNN generated the best predicted welding characteristics.Analysis under various welding conditions also shows a mapping relationship among welding deformation,temperature,and residual stress over a period of time.This finding further provides a paramount basis for the control of welding assembly errors of an antenna structure in the future.
基金This project is supported by National Natural Science Foundation ofChina(No.l9832020) and National Outstanding Youth Science Foundation ofChina(No.10125208).
文摘A physical value mapping （PVM） algorithm based on finite element mesh from the stamped part in stamping process to the product is presented, In order to improve the efficiency of the PVM algorithm, a search way from the mesh of the product to the mesh of the stamped part will be adopted. At the same time, the search process is divided into two steps： entire search （ES） and local search （LS）, which improve the searching efficiency. The searching area is enlarged to avoid missing projection elements in ES process. An arc-length method is introduced in LS process. The validity is confirmed by the results of the complex industry-forming product.
基金supported by the National Natural Science Foundation of China(Grant No.50579081)EPSRC UK(Grant No.EP/F00656X/1)+1 种基金the State Key Laboratory of Water Resources and Hydropower Engineering Science,Wuhan University,China through an open Research (Grant No.2010A004)Zhang's one-year research visit to the University of Liv-erpool was funded by China Scholarship Council
文摘The scaled boundary finite element method(SBFEM) is a semi-analytical numerical method,which models an analysis domain by a small number of large-sized subdomains and discretises subdomain boundaries only.In a subdomain,all fields of state variables including displacement,stress,velocity and acceleration are semi-analytical,and the kinetic energy,strain energy and energy error are all integrated semi-analytically.These advantages are taken in this study to develop a posteriori h-hierarchical adaptive SBFEM for transient elastodynamic problems using a mesh refinement procedure which subdivides subdomains.Because only a small number of subdomains are subdivided,mesh refinement is very simple and efficient,and mesh mapping to transfer state variables from an old mesh to a new one is also very simple but accurate.Two 2D examples with stress wave propagation were modelled.The results show that the developed method is capable of capturing propagation of steep stress regions and calculating accurate dynamic responses,using only a fraction of degrees of freedom required by adaptive finite element method.
基金Project supported by the General Program of National Natural Science Foundation of China (51874062)。
文摘To study the hot deformation behavior of Mg-8.3 Gd-4.4 Y-1.5 Zn-0.8 Mn(wt%) alloy,hot compression tests were conducted using a Gleeble-3500 thermal simulator at temperatures ranging from 653 to773 K,true strain rates of 0.001-1 s^(-1),and a deformation degree of 60%.Results of hot compression experiments show that the flow stress of the alloy increases with the strain rate.The true stress-true strain curves are corrected by correcting the effect of temperature rise in the deformation process.Activation energy,Q,equal to 287380 J/mol and material constant,n,equal to 4.59 were calculated by fitting the true stress-true strain curves.Then,the constitutive equation was established and verified via finite element simulation.Results of the hot processing map show that the probability of material instability increases with the degree of deformation,which indicates that the material is not suitable for large deformation in a single pass.On the whole,the alloy is appropriate for multipass processing with small deformation and a suitable processing temperature and strain rate are 733 K and 0.01 s-1,respectively.
基金Open access funding provided by Lund University.
文摘Axially heterostructured nanowires are a promising platform for next generation electronic and optoelectronic devices.Reports based on theoretical modeling have predicted more complex strain distributions and increased critical layer thicknesses than in thin films,due to lateral strain relaxation at the surface,but the understanding of the growth and strain distributions in these complex structures is hampered by the lack of high-resolution characterization techniques.Here,we demonstrate strain mapping of an axially segmented GalnP-lnP 190 nm diameter nanowire heterostructure using scanning X-ray diffraction.We systematically investigate the strain distribution and lattice tilt in three different segment lengths from 45 to 170 nm,obtaining strain maps with about 10^-4 relative strain sensitivity.The experiments were performed using the 90 nm diameter nanofocus at the NanoMAX beamline,taking advantage of the high coherent flux from the first diffraction limited storage ring MAX IV.The experimental results are in good agreement with a full simulation of the experiment based on a three-dimensional(3D)finite element model.The largest segments show a complex profile,where the lateral strain relaxation at the surface leads to a dome-shaped strain distribution from the mismatched interfaces,and a change from tensile to compressive strain within a single segment.The lattice tilt maps show a cross-shaped profile with excellent qualitative and quantitative agreement with the simulations.In contrast,the shortest measured InP segment is almost fully adapted to the surrounding GalnP segments.
基金supported by the US Army 62151-MA,DOE and NSF(DMS 0934837,DMS 0724704,and DMS 0811180)supported by Award No.KUS-C1-016-04,made by King Abdullah University of Science and Technology(KAUST).
文摘In this paper,we present the Multiscale Finite Element Method(MsFEM)for problems on rough heterogeneous surfaces.We consider the diffusion equation on oscillatory surfaces.Our objective is to represent small-scale features of the solution via multiscale basis functions described on a coarse grid.This problem arises in many applications where processes occur on surfaces or thin layers.We present a unified multiscale finite element framework that entails the use of transformations that map the reference surface to the deformed surface.The main ingredients of MsFEM are(1)the construction of multiscale basis functions and(2)a global coupling of these basis functions.For the construction of multiscale basis functions,our approach uses the transformation of the reference surface to a deformed surface.On the deformed surface,multiscale basis functions are defined where reduced(1D)problems are solved along the edges of coarse-grid blocks to calculate nodalmultiscale basis functions.Furthermore,these basis functions are transformed back to the reference configuration.We discuss the use of appropriate transformation operators that improve the accuracy of the method.The method has an optimal convergence if the transformed surface is smooth and the image of the coarse partition in the reference configuration forms a quasiuniform partition.In this paper,we consider such transformations based on harmonic coordinates(following H.Owhadi and L.Zhang[Comm.Pure and Applied Math.,LX(2007),pp.675-723])and discuss gridding issues in the reference configuration.Numerical results are presented where we compare the MsFEM when two types of deformations are used formultiscale basis construction.The first deformation employs local information and the second deformation employs a global information.Our numerical results showthat one can improve the accuracy of the simulations when a global information is used.
